In this work, efficient synthesis of 9-aryl-1,8-dioxo-octahydroxanthene derivatives from 1,3-cyclohexanediones and arylaldehydes in the presence of catalytic amount of melamine trisulfonic acid (MSTA) is described. The reaction is studied under thermal (solvent-free/80 °C),microwave (solvent-free/180 W/90 °C) and ultrasound (solvent/34-37 kHz/350 W/60 °C) conditions.